1. Field of the Invention
Embodiments of the present invention generally relate to the fabrication of integrated circuits. More specifically, embodiments of the present invention generally relate to processes for depositing barrier layers on a substrate and structures that include the barrier layers.
2. Description of the Related Art
Semiconductor device geometries have dramatically decreased in size since such devices were first introduced several decades ago. Since then, integrated circuits have generally followed the two year/half-size rule (often called Moore's Law), which means that the number of devices that will fit on a chip doubles every two years. Today's fabrication plants are routinely producing devices having sub-quarter micron feature sizes, and tomorrow's plants soon will be producing devices having even smaller geometries.
In order to further reduce the size of devices on integrated circuits, it has become necessary to use conductive materials having low resistivity, such as copper, and insulators having low k (dielectric constant <4.0) to reduce the capacitive coupling between adjacent metal lines.
A barrier layer is typically deposited between subsequently deposited conductive materials and low k dielectric material to prevent diffusion of byproducts such as moisture onto the conductive materials. For example, moisture that can be generated during formation of a low k insulator readily diffuses to the surface of the conductive metal and increases the resistivity of the conductive metal surface.
A barrier layer can also be used to prevent diffusion of conductive materials. Low k dielectric materials are often porous and susceptible to interlayer diffusion of conductive materials, such as copper, which can result in the formation of short-circuits and device failure. A barrier layer is typically used in copper damascene structures to reduce or prevent interlayer diffusion.
Attempts have been made to deposit silicon carbide barrier layers by plasma enhanced chemical vapor deposition. However, silicon carbide barrier layers typically have had undesirable characteristics, such as unacceptable current leakage, and film instability, such as upon exposure to air. Silicon carbide layers doped with oxygen or nitrogen have shown some improvements in the areas of current leakage, compressive stress, and film stability. However, the nitrogen in nitrogen-doped silicon carbide layers can poison photoresist layers deposited on a substrate. The gases used to incorporate oxygen in oxygen-doped silicon carbide layers can oxidize underlying metal features on which the oxygen-doped silicon carbide layer is deposited.
Therefore, there remains a need for methods of depositing silicon carbide and oxygen-doped silicon carbide barrier layers with good chemical and mechanical properties.